Education reform has come under attack lately, and not just from the usual suspects. Some of the critics are reformers themselves. Others have responded that reform is working just fine. But few on either side are acknowledging the three basic mistakes that have undermined the success of the reform movement from its inception.

The recent criticism has been spurred by reports that the soaring graduation rate in Washington, D.C.—a city long hailed as a national model for education reform—hid the fact that many students had been promoted from grade to grade when they shouldn’t have been. An investigation revealed that over a third of last year’s D.C. public school graduates weren’t entitled to receive diplomas—and, according to at least one teacher, some were unable to read and write.

Photographer: Scott Eisen/Bloomberg

D.C., it seems, is not an isolated case. Similar scandals have emerged elsewhere, and teachers around the country have reported pressure to pass students who flunked their classes or simply didn’t show up. All of this has led someeducationreformers to charge that the successes that have been celebrated by the movement for years are largely a mirage.

In response, defenders like Arne Duncan—who pushed many of the reforms as Secretary of Education in the Obama administration—argue that there has been real progress. In a Washington Post op-ed published earlier this month, Duncan pointed to—among other things—gains in fourth- and eighth-grade reading and math scores since 1971, with much of the increase coming from students of color.

Although he also cites the record-high national graduation rate—a dubious figure, in light of the scandals in D.C. and elsewhere—Duncan is not completely wrong. At least in some areas, school systems are no longer the dysfunctional mess they were 15 years ago. For example, in D.C.—where I happen to live—it used to be the case that textbooks remained in warehouses, teachers didn't get their paychecks, and many schools were in a shocking state of disrepair. And while the overall impact of charter schools is debatable, thousands of students have clearly benefited from the chance to attend those that are high-performing.

But on closer examination, the test scores Duncan and others cite as evidence of success actually tell a story of unfulfilled promises. Most of the gains occurred in the 1990s and early 2000s, and researchers have concluded that few are attributable to the federal No Child Left Behind legislation that ushered in the current era of high-stakes testing. Math scores did rise significantly between 1998 and 2009 but have been largely flat ever since—and reading scores have been stagnant since 1998. Even more troubling, scores for high school students have been flat or declining in both reading and math since the early 1970s.

There is evidence that the gap in scores between white students and students of color has narrowed somewhat. At the same time, though, the gap between the scores of higher- and lower-income students has only expanded—a fact that Duncan fails to mention.

As for the lack of progress at the high school level, he suggests that lower-achieving kids aren’t dropping out as much as they used to—in which case the flat scores are “arguably a victory.” Alternatively, he says vaguely, maybe “high schools have simply been more resistant to reform.” Any narrative that casts doubt on the success of education reform, he concludes, is motivated by “politics.”

But high school results are crucial: the point of reform isn’t just to produce fourth- and eighth-graders who do well on tests. It’s hardly a “victory” to graduate students who are functionally illiterate, as has been happening in D.C. and elsewhere. And what is it about high schools that make them “more resistant to reform”? Are the teachers just uncooperative?

In fact, both the lack of progress at upper grade levels and the stubborn gap between wealthier and poorer students are the results of three basic—and erroneous—assumptions that reformers have long embraced:

1. The real problems begin at the high school level. In fact, the problems that manifest themselves in high school have their roots in elementary school, which reformers have long seen—mistakenly—as the bright spot in education. When students arrive in ninth grade reading several years below grade level, as is often the case in high-poverty schools, the answer is not simply to demand that they graduate within four years, come hell or high water. We need to give students more time to catch up if they need it—and we need to start looking critically at what is happening before high school that leaves students so unprepared.

2. The most important factor in educational achievement is a highly effective teacher. It’s true that teachers are hugely important, but reformers have judged teachers’ effectiveness by how much they boost students’ test scores and whether they’re seen to be employing the right kind of classroom “moves.” What reformers have paid little or no attention to is what teachers are being asked to teach. There’s increasing evidence that the best way to improve teachers’ performance is to provide them with high-quality instructional materials and specific training in how to use them.

3. Education needs to be data-driven. What this means in practice is two-fold. First, teachers and schools are held accountable at least partly on the basis of students’ end-of-year scores on math and reading tests. In addition, teachers give students tests throughout the year that are supposed to predict performance on end-of-year tests, and they base their instruction on the results. At least when it comes to reading tests, this approach is actually counterproductive.

Standardized tests are important in illuminating broad trends and inequities between demographic groups, but they shouldn't be used to guide reading instruction. Reading tests purport to test reading comprehension “skills” such as “making inferences” and “finding the main idea.” So that’s what teachers spend many hours a day trying to teach, especially in schools with low test scores, throughout elementary and sometimes middle school. Reading and math have taken over the curriculum in many schools, to the exclusion of subjects like history and science.

Herein lies much of the explanation for the lack of progress at the high school level: If students have learned nothing about history or science before they arrive, they’re hardly going to be equipped to do high school level work.

The focus on comprehension skills also helps explain the income-based test score gap. Standardized tests ask students to read passages on a variety of topics, with no regard to whether they match what students have learned in school. That means the tests are essentially assessments of general knowledge and vocabulary. The more knowledge you have, the more likely it is that you'll actually understand the passages and have a chance to demonstrate your skills. And especially when schools aren't even trying to build students' knowledge, the children of wealthier parents are more likely to acquire knowledge and vocabulary outside of school.